Non-thrombogenic material

ABSTRACT

Non-thrombogenic material comprising a base polymer treated with heparin, the improvement in which the heparin is covalently bonded with the base polymer through only one acetal bond or hemiacetal bond at each bonding site between the heparin and the base polymer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to non-thrombogenic material, and particularlyrelates to polymeric material heparinized through covalent bonds. Saidinvention is particularly concerned with a novel procedure for producingsaid non-thrombogenic material.

2. Description of the Prior Art

In general, contact of the blood with nearly any foreign surface leadsto blood coagulation. This problem would severely limit the use of manyotherwise useful medical procedures. The coagulation is initiatedthrough an activation factor (also known as Hoegeman factor or FactorXII) that activates clotting factors culminating in polymerization offibrinogen to fibrin. This surface-induced coagulation has presentedobvious difficulties in such therapeutic procedures as the use of anartificial kindney, heart, lung etc. Without systemic anticoagulats suchas heparin, their use would have been impossible. Similarly, heartvalves made from metals and polymeric materials produce emboli so thatit is necessary to maintain patients on anti-coagulant therapyindefinitely.

In other procedures, for example, catheterization and blood shunting, achoice has had to be made between the systemic heparinization and therisk of clot formation. Systemic anticoagulation is, of course, not asatisfactory answer due to control problems and the posibility ofhemorrhage. In spite of all the foregoing difficulties, it is well knownthat artificial kidneys and blood oxygenators have been widely used.This is only made possible by administration of heparin, nature's ownanticoagulant, into the patient's blood stream. Such procedures toprevent clotting are of a short-term nature, since the heparin isultimately dissipated by the body. Thus, it has long been desirable thata material possessing long-term non-thrombogenic effect be materialized.

The first significant advance toward permanently non-thrombogenicsurface has come with the development of heparinized surface by Gottet.al. (Gott, V. L., Whiffen, J. D. and Dutton, R., Science 142, 1297(1963)). In their procedure, graphite is first coated on the polymersurface. The graphite, in turn, serves to absorb a cation, usuallybenzalkonium group, which then ionically binds heparin molecule. Themethod of binding heparin on to the surface of a polymeric materialthrough a quaternized amine has been further developed by otherresearchers. In one instance, phenyl groups of polystyrene arechloro-methylated, quarternized with dimethylaniline and then subjectedto binding with the heparin. In the above reaction, the heparin isbonded only ionically as a quarternary ammonium salt. The ionicallybonded heparin does, in fact, slowly dissociate from the surface in thepresence of blood. This means that anti-coagulant properties obtainedwith ionically-bonded heparin are of a short-term nature.

There have been several attempts with limited success to link or bindheparin covalently to a certain polymer. For example, polyvinyl alcoholis allowed to react with the heparin in the presence of a dialdehydesuch as glutaraldehyde. This utilizes the reaction between the aldehydesand the hydroxyls on the adjacent carbon atoms to form 6-membered1,3-dioxane ring. The procedure can link the heparin to the polymer witha covalent bond, from which permanent non-thrombogenic properties may beexpected. The vital drawback of the above procedure lies in the factthat the bi-functional dialdehyde does not always react only between theheparin and the polyvinyl alcohol, but, more likely, reacts between theheparin molecules and also reacts between the polyvinyl alcoholmolecules to form many heparin-heparin and polyvinyl alcohol-polyvinylalcohol cross-linkages. This reaction procedure develops cross-linkedheparin gels or the cross-linked polyvinyl alcohols. These products are,of course, unfavorable (undesired) by-products. The ideal picture of thereaction is that one aldehyde in the dialdehyde molecule reacts with theheparin while another aldehyde reacts with the polyvinyl alcohol so thatthe heparin and the polyvinyl alcohol are bonded each other throughaldehyde-OH reaction. Also, as has been known the anti-coagulant effectof the heparin is remarkably reduced by chemical modifications.Therefore, the linking of the heparin and the polyvinyl alcohol by theaction of the dialdehyde can not be called "successful" in view of thenon-thrombogenic property obtained is less then one would expect.

SUMMARY OF THE INVENTION

An object of this invention is to provide non-thrombogenic materialscovalently linked with heparin without the formation of a by-product,and a method for producing such non-thrombogenic materials.

Another object of this invention is to provide a hollow fiber withlong-term non-thrombogenic properties when exposed to blood, and amethod for producing such hollow fiber.

A further object of this invention is to provide a method for producingnon-thrombogenic materials which involves a reaction between heparin andaldehyde-containing polymers.

A still further object of this invention is to provide a method forproducing non-thrombogenic materials between heparin and analdehyde-containing polymer which is prepared by the cleavage ofcarbon-carbon bond by the reaction of periodic acid (or its salt) orlead tetraacetate to give aldehyde groups.

A still further object of this invention is to provide a medical devicehaving non-thrombogenic properties.

A still further object of this invention is to provide a method forproducing non-thrombogenic medical devices which are used in contactwith blood, such as artificial kidney, heart, lung, devices inintravascular implantation or extra corporeal connections or prostheses,and membranes for blood dialysis, blood filtration and oxygenation.

According to an aspect of this invention, the invention is directed tonon-thrombogenic material comprising a base polymer treated withheparin, in which the heparin is covalently bonded with the base polymerthrough only one acetal bond or hemiacetal bond at each bonding sitebetween the heparin and the base polymer.

The above and other objects, features and advantages of this invention,will be apparent in the following description and examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention relates to a method for producing non-thrombogenicmaterials which involves a reaction between heparin and an aldehydegroup-containing polymer. This invention differs from the prior art,which has been directed to linking heparin and a polymer by the functionof a dialdehyde, in that the present invention does not involveundesirable side reactions such as heparin-heparin bonding orpolymer-polymer bonding. Therefore, there are no unfavorable gelledmaterials formed as by-products and, probably because of the minimumchemical modification of the heparin, non-thrombogenic properties of thecomposition of this invention are out-standing. This is surprising fromthe fact that it has been observed that the anti-coagulant function ofheparin is appreciably decreased by any sort of chemical modification.

In practice of the present invention, the "aldehyde group-containingpolymer" can be prepared by the polymerization or copolymerization ofthe monomer which has an aldehyde or aldehyde group-forming group,namely, acetal or hemiacetal group. Thus, the "aldehyde group containingpolymer" means the polymer containing aldehyde group or aldehydegroup-forming group such as acetal or hemiacetal along the polymerchain.

Examples of these monomers are acrolein, methacrolein, p-formyl stryene,N-formyl amino ethyl acrylamide, N-formyl ethyl acrylamide, formyl ethylacrylamide, formyl ethyl methacrylate, ketene dimethyl acetal, ketenediethyl acetal, acrolein acetal, methacrolein acetal and so forth. Thepolymerization or copolymerization of this kind of the monomer withother copolymerizable vinyl compounds can be performed in the usualmanner by using a common radical initiator. An example of thecopolymerization is given below to form "aldehyde group-containingpolymer". Allylidene diacetate (CH₂ ═CH--CH (OAc)₂) prepared by thereaction between acrolein and acetic anhydride can be copolymerized withanother vinyl compound like vinyl acetate, which is subsequentlyhydrolyzed to a "aldehyde group-containing polymer" as follows: ##STR1##Other monomer such as vinyl chloride, acrylonitrile, methacrylonitrile,methyl methacrylate, isopropyl methacrylate, isopropenyl acetate, methylmethacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate,methacrylic acid, acrylic acid, styrene, α-methyl styrene may be usedfor copolymerization with "aldehyde group-containing monomer". The"aldehyde group-containing polymer" may be prepared, in turn, byperiodic acid (or its salt) or lead tetraacetate cleavage ofcarbon-carbon bonds, which is a characteristic reaction of carbon-carbonbonds, where adjacent carbon atoms possesses --OH group, i.e.,vic-glycol. The typical polymers having vicinal hydroxyl group can benatural polymers having glucose units. The natural polymers may becellulose, cellulose derivatives such as oxycellulose, benzyl cellulose,cyanoethyl cellulose, cellulose acetate, polysaccharide, starch, gumarabic chitin, chitosan, galactane, arabane galactomannane, xylane,alginic acid (or its salt), heparin and so forth.

These natural polymers have repeating glucose units in the chainmolecule. The glucose unit has vic-glycol which can be cleaved by theaction of periodic acid (or its salt), or lead tetraacetate as follows:##STR2## Therefore, by treating with periodic acid, the polymer havingglucose units can be easily converted "aldehyde group-containing polymer("P-CHO" will be used short for "aldehyde group-containing polymer".) bythe simple treatment with periodic acid or lead tetraacetate. In thecase of cellulose, the reaction can be visualized as follows: ##STR3##

On the other hand, chemical structure of heparin has the repeating unitdescribed below: ##STR4## Heparin also vic-glycol in the chain.Hereafter we use simplified formula ##STR5## for heparin. The vic-glycolin the heparin molecule reacts with aldehyde in the acidic medium. Thus,the reaction between vic-glycol of the heparin and the aldehyde group inthe polymer forms 5-membered ring, i.e., dioxolane ring which is verystable by nature, in accordance with the following reaction: ##STR6##The hemiacetal structure is likely to be converted to more stable acetalby elimination of one water molecule.

The aldehyde group in the polymer may be converted to acetal orhemiacetal in the presence of alcohol as follows: ##STR7## The chemicalreactivity of acetal or hemiacetal shown above does not make anydifference from "free" aldehyde, and these react with heparin in thesame way as "free" aldehyde. ##STR8## When the reaction (1) is carriedout in an acidic medium in the presence of alcohol, hemiacetal structuremay be formed. ##STR9## But this structure is liable to react further toform stabler 1,2-dioxolane ring by liberating ethanol. ##STR10## Thus,the reaction in this invention can be summarized as follows: ##STR11##By the above reaction, heparin and the "aldehyde group-containingpolymer" can be covalently bonded, which means that the linked heparindoes not dissociate, thus, the heparin can not be leach out when exposedin the blood stream. In this reaction, there is neither aheparin-heparin side reaction, nor a polymer-polymer reaction as occursto great extent in the prior art.

In the present invention, from the principle of the above reaction, onecan understand that any polymer which has aldehyde or acetal group canbe obviously used. The polymer may be a homopolymer, copolymer, blockcopolymer or a graft copolymer and blends of the above polymers.

The aldehyde group-containing polymer contains preferably aldehyde groupranging from 1.0 to 20.0% by weight of the polymer, and heparin solutionpreferably has 50 to 100,000 USP unit heparin when applied to thereaction.

The above reaction can be carried out in a homogeneous phase or in ahetero geneous phase. For example, a water soluble starch is dissolvedin water to form a homogeneous solution, treated with sodium metaperiodate, then allowed to react with heparin in an acidic medium. Onthe other hand, the surface of medical device which is exposed to bloodcan be coated with the above reaction product which can be renderedinsoluble by the cross-linking with a dialdelyde such as glyoxal orglutaraldehyde. The invention may also be applied to any shaped articlemade from cellulose. For example, the interior of a cellulose hollowfiber, or cellulose tube may be treated with periodic acid to formaldehyde groups, followed by the above-described treatment with heparincellulose film may also be treated in the same way.

The polymer treated is not always limited to a sole polymer, but may bea composite material or a blend material. This invention may be appliedon the surface of a shaped article which is exposed to blood when inuse. Thus, the coating material having aldehyde group which can coverforeign surface may be utilized.

In the case of cellulose hollow fiber, the present invention may beapplied in a hollow fiber manufacturing process. The inventor hasalready disclosed a novel method for producing cellulosic hollow fiber.According to his above-mentioned disclosure, cellulose ester, preferablycellulose acetate is dissolved in an organic solvent, for example,acetone. The hollow fiber can be spun through a "tube in orifice"spinnerete. The key to the success for forming the hollow fiber at ahigh speed (200 m/min) lies in the fact that a core solution whichcontains an effective amount of a salt which plays an important role indeveloping phase separation between the core solution and the spinningdope is used. Examples of said water soluble salt are sodium chloride,potassium chloride, calcium chloride, sodium phosphate, ammoniumchloride, sodium acetate, sodium oxylate and so forth. When thistechnique is applied in the dry-jet wet spinning method, the spun-dopefilament from the orifice is not gelled during the dry passage becausethe phase separation prevents the diffusing of the core solution intothe sheath dope filament. Therefore, the spun dope-filament can beeasily stretched during the air gap before being introduced into thecoagulation bath.

The present invention may also be applied to the above hollow fiberproducing process. When the core solution contains sodium metaperiodate, for example, in the form of mixture with another watersoluble salt such as sodium chloride, calcium chloride or sodiumacetate, the inner surface or the hollow surface of the filament iscontacted with sodium meta periodate which selectively attacksvic-glycol of the cellulose ester to develop aldehyde groups. The coresolution can contain alkali metal hydroxide such as sodium hydroxide orpotassium hydroxide. In this case, the inner surface or the hollowsurface can be simultaneously hydrolyzed so as to regenerate cellulose,which is attacked simultaneously by the periodate to give rise toaldehyde group. Preferable concentration of periodic acid or its salt inthe core solution is 0.01 to 3 mol/l and more preferably 0.05 to 1.0mole/l. When the concentration is lower than 0.01 mole/l, reaction willnot proceed satisfactory, and, when concentration is more than 3.00mole/l, degradation due to cleaverage of cellulose molecule may takeplace. The core solution may be acidic, for example, the core solutioncan contain periodic acid. This acidic core solution can contain otherinorganic or organic acids, such as hydrochloric acid, nitric acid,sulfuric acid or acetic acid. The solution also may contain neutralsalts or acidic salts such as sodium chloride, potassium chloride,ammonium chloride, ammonium bromide and so on.

The hollow fiber thus formed can be successively treated with heparin inan acidic medium. Thus, heparin can be linked co-valently on the innersurface of the hollow fiber. The follow fiber thus obtained has along-term, almost permanent non-thrombogenicity, which has long beenneeded.

The core solution may be an organic liquid which does not gel thespinning solution, namely, a liquid having a swelling effect for thedope-polymer, or a solvent for the dope polymer. In this case, the coresolution does not coagulate the spinning dope during the dry-passage (orin the air gap) when applied to dry-wet jet spinning method. The spundope can be stretched before being introduced into the coagulation bath,where gellation take place instantaneously. This makes the spinningspeed extremely high (180 m/min), compared to the known process. Theexample of this type of core solution may be formamide, dimethylsulfoxide, dimethyl acetamide, dimethyl formamide, γ-butyrolactonetetramethylene sulfone, 2-pyrrolidone, or mixtures of the abovecompounds, for cellulose acetate as dope polymer. These core solutioncan contain heparin to react based on the same principle.

The principle presented in the present invention can also be applied ina different mode. Heparin, which also contains vic-glycol, is firsttreated to form aldehyde in its molecule as follows: ##STR12## Theproduct can react with a polymer having vicinal hydroxyl group such ascellulose or polyvinyl alcohol as follows: ##STR13## When the hydroxypolymer is cellulose, the heparin is linked through a 5-memberedsubstituted dioxolane ring: ##STR14## When the hydroxy polymer ispolyvinyl alcohol, the acetal linkage is in the form of 6-memberedsubstituted 1,3-dioxane ring: ##STR15## The both 5- and 6-memberedacetal rings are very stable by nature, thus, the heparin molecules arebonded firmly by the covalent bonds. This is the reason why the abovereaction products have long-term thrombogenicities.

The procedure presented in this invention can be applied in any form ofthe shaped articles. The invention also is applied as a coating materialwhich has previously been subjected to this invention to link heparin.Also the present invention can be applied after being coated with thepolymer having vic-glycol or aldehyde (or acetal) groups, through saidfunctional groups. The heparin can be bonded as described in detailsupra. Heparin can be bonded as described in detail before.

This invention is further illustrated in and by the following exampleswhich are given merely as illustration and are not intended to restrictin any way the scope of the invention nor the manner in which it can bepracticed.

EXAMPLE 1

Sodium meta periodate was dissolved in 100 ml of water and the solutionthus obtained was maintained at 5° C. Into this solution, a commercialcuprophane film prepared from cuproammonium solution was immersed for 30minutes, then washed with distilled water and dried at ambienttemperature. The film was next immersed in 50 ml of an aqueous solutioncontaining 25,000 unit/ml heparin for 30 minutes at 40° C. The heparinsolution was adjusted at pH 4 with sulfuric acid. After being treated inthe heparin solution, the film was washed with water again, and dried atambient temperature.

EXAMPLE 2

A 100 ml of aqueous solution having 0.01 mole of sodium meta periodatewas adjusted to pH 8 with H₂ SO₄. The solution was placed in the darkplace at 10° C. Into this solution, the commercial cellophane film wasimmersed and allowed to react for 20 minutes. Then, the film wasthoroughly washed with distilled water. The film was then allowed toreact with heparin by being immersed in the aqueous solution having5,000 unit/ml of heparin at pH of 3. Temperature was maintained at 50°C. during the reaction. After ten minutes, the film was taken up fromthe solution, washed with sufficient ammount of distilled water and thendried at ambient temperature.

EXAMPLE 3

50 g of water soluble starch was dissolved in 300 ml of water and thesolution obtained was maintained at 30° C. To this solution, an aqueoussolution (50 ml) containing 1 g of sodium meta periodate was added, andthe mixture was stirred for 10 minutes. The reaction product wasprecipitated by pouring the reaction mixture into large excess ofmethanol. The precipitant was filtered, and then it was dissolved inwater again. After the aqueous solution thus obtained had been adjustedto pH 3.5 with H₂ SO₄, 5 ml of solution having 25,000 unit/ml of heparinwas added, and the solution was allowed to react at 40° C. for 30minutes. The reaction mixture was again precipitated in a large excessof methanol under agitation. The precipitant was sufficiently washedwith methanol. Purification of the reaction product was performed byreprecipitation using water-methanol system. Thus, heparinized starchwas obtained.

Using a tube made from polyvinyl chloride (100 mm long and 10 mm ininner diameter), a test tube was prepared by closing one end of thetube. The heparinized starch obtained above was dissolved in water toform a 25% solution; the pH thereof was adjusted to 1.0 with H₂ SO₄ andan amount of glutaraldehyde calculated to form a 3% solution was addedthereto. Immediately after the addition of the glutaraldehyde, thesolution was poured into the polyvinyl chloride test tube, then the tubewas rotated so that the inner surface was covered uniformly with thesolution. After this operation, excess solution was decanted, then thetube was dried at 50° C. As the result, the inner surface was uniformlycoated with cross-linked, heparinized starch.

Another experiment was conducted as follows, using soft-polyvinylchloride film containing dioctyl phthalate (DOP) as a plasticizer:Immediately after the addition of glutaraldehyde to the acidic aqueoussolution of the heparinized starch, the aqueous solution was coated onthe surface of the film described in Example 2, then the coated film washeat-treated at 60° C. to evaporate water therefrom. As a result,glutaraldehyde-cross-linked heparinized starch, which is no longersoluble in water, was uniformly coated on the surface of the film. Afterbeing washed with a sufficient amount of water to eliminate the solubleportion, the film was dried at ambient temperature.

EXAMPLE 4

Using a tube made from cellulose butyrate acetate by Eastman Kodak Co.,the following experiment was carried out. First, the inner surface ofthe tube was treated with 3 normal aqueous solution. By this procedure(KOH treatment), the inner surface of the tube was partly hydrolyzed toregenerate cellulose. After being washed thorughly with water, the innersurface of the tube was contacted with the aqueous solution of sodiummeta periodate as in example 1 at 5° C. in dark place. After this, theperiodate solution was removed from the tube which was then washed withwater. The water-washed tube was then immersed in an aqueous solutioncontaining 10,000 unit/ml of heparin at pH 3 for 30 minutes at 40° C.The tube was then washed with water and dried.

EXAMPLE 5

Anti-coagulant tests were carried out using surface-heparinized filmobtained in the examples 1 to 3. The following tests were employed. Forcomparison, un-heparinized films of the same materials were tested ascontrols. The test for non-thrombogenetic properties was made by twomethods described below:

The First Method (Test I)

The film was first thoroughly washed with the saline solution, thenplaced on a watch glass. On this film, 1 ml of the fresh human blood wasplaced, then the test was made in such a manner that the silicon-coatedneedle was tipped into the blood and pulled up, and checked if anyfibrous material may be pulled up with the needle or not. The time thatthe fibrous material was first observed was defined as the initialcoagulating time. The complete coagulation time was defined as the timethat the blood was no longer flow down when the watch glass was tiltedand tipped over.

The Second Method (Test II)

This test was carried out using dog's ACD blood. For one sample, 5pieces of film were prepared and placed in watch glasses independently.These are kept at 37° C., then the fresh dog's ACD blood (0.25 ml each)was placed on every pieces of the films. Immediately after this, theaddition of 0.025 ml of aqueous CaCl₂ solution, the concentration ofwhich was 0.1 mole/l, was followed. This will start coagulation of theblood. After appropriate time intervals, coagulated blood mass was fixedwith formation. This was again washed with water. After removing thewater, the blood mass was weighed. The weight percent of the blood massbased on the control means which was prepared in the same condition onthe glass plate.

The results oftained are summarized in the following table.

    ______________________________________                                                       Test I                                                         Test Sample    Coagulation Time                                                                              Test II                                        Kind    Heparinized                                                                              Initial   Complete                                                                              Blood Mass                               ______________________________________                                        Example 1                                                                             yes        300 min   >10 hrs 3%                                               no          11 min   16 min   81%                                     Example 2                                                                             yes        240 min   >10 hrs 6%                                               no          10 min   19 min   89%                                     Example 3                                                                             yes        240 min   >10 hrs 8%                                               no          8 min    14 min   72%                                     Glass plate                                                                           no          6 min    12 min  100%                                     (control)                                                                     ______________________________________                                    

From the above results, it is obvious that the heparinization in thepresent invention shows outstanding effect.

EXAMPLE 6

In this example, the tests of coagulation of the blood were examinedusing Lee-White method. Specimens used in this example were polyvinylchloride tube coated with the heparinized starch obtained in the Example3, and the partly hydrolyzed and heparinized cellulose acetate butyratetube obtained in Example 4. For comparison, unheparinized tube specimensof the same kind, and glass test tubes with and without the treatmentwith silicone were tested in the same condition. The results aresummarized in the following table.

    ______________________________________                                        Tube Specimen        Coagulation                                              Kind          Heparinized                                                                              Start Time                                           ______________________________________                                        Example 3     yes        >5 hrs                                                             no         16 min                                               Example 4     yes        >5 hrs                                                             no         10 min                                               Glass tube*   --          8 min                                               Glass tube**  --         32 min                                               ______________________________________                                         *without treatment with silicone                                              **treated with silicone                                                  

REFERENCE EXAMPLE 1

215.2 mg of sodium heparin was dissolved in 100 ml of distilled water.To this, 0.0624 mole of sodium meta periodate was added, and the mixturewas kept for 28 hours at 5° C. By this procedure, one glycol per 16glucose units of heparin was cleaved on an average. This solution wasused as solution (I). After this solution was maintained for anadditional 20 hrs in the dark, two glycols per 16 glucose units ofheparin were cleaved. This solution was used as the solution (II).

EXAMPLE 7

The commercial Cuprophan® and Cellophan® film were cut to square (5×5cm). The films were treated with solutions (I) and (II) at pH 3 adjustedwith H₂ SO₄ for 60 min. Temperature was maintained at 60° C. The filmswere then washed with water and dried.

EXAMPLE 8

A polyvinyl alcohol aqueous solution was prepared using a commercialpolyvinyl alcohol. From the solution, a polyvinyl alcohol film wasprepared by usual casting method. After heat-treatment of the film at80° C. for 4 hours, the film became insoluble in water because of thecrystallization. This film was treated at pH 1.0 for 4 hours at 50° C.with solution (I).

EXAMPLE 9

A film made from a copolymer of vinyl acetate-ethylene copolymer wastreated in a KCl saturated aqueous solution with 1 N of potassiumhydroxide for 1 hour at 40° C. The surface of the film was hydrolyzed,which was confirmed by IR spectrum, showing the presence of -OH group.This surface-hydrolyzed film was treated with solution (II) at pH 1.0for 1 hour at 40° C. The film was then washed with water and dried.

EXAMPLE 10

A commercial vinyl chloride-ethylene-vinyl acetate graft copolymer(GRAFTMER® from the Nippon Zeon Co.) was shaped into a tube. Theinterior of the tube was hydrolyzed by contact with 2 normal potassiumhydroxide aqueous solution. Thus interior surface of the tube becamevinyl chloride-ethylene-vinyl alcohol copolymer. After being washedsufficiently, the tube was treated with solution (I) at pH 3 for 1 hour.Temperature was maintained at 30° C. After being washed with H₂ O, thetube was cut to 10 cm length, and one end of the tube was heat-closed toform a test tube.

EXAMPLE 11

A tube from cellulose butyrate acetate was surface-hydrolyzed in thesame manner as in Example 10. After being washed thoroughly with water,the tube was treated with solution (II) at 30° C. for 1 hour at pH 4.0.

EXAMPLE 12

Using the specimens obtained from Examples 7 to 11, non-thrombogenicproperties were examined by the method proposed in Example 5. Theresults obtained are summerized in the following table.

    ______________________________________                                                       Test I                                                         Test Specimen  Coagulation time                                                                              Test II                                        kind    Heparinized                                                                              Initial   Complete                                                                              Blood Mass                               ______________________________________                                        Example 7                                                                             yes        230 min   >10 hrs 3%                                               no          8 min    12 min   82%                                     Example 8                                                                             yes        300 min   >10 hrs 6%                                               no          6 min    17 min   91%                                     Example 9                                                                             yes        120 min   >10 hrs 8%                                               no          5 min    14 min   88%                                     Glass   --          8 min    14 min  100%                                     ______________________________________                                    

From the above results, the effect of the present invention is obvious.

EXAMPLE 13

The tubes obtained by Examples 10 and 11 were tested by Lee-Whitemethod. For comparison, glass tubes were tested with and withoutsilicone treatment. The results are summarized in the following table.

    ______________________________________                                        Tube Specimen                                                                 Kind        Heparinized                                                                              Coagulation Start Time                                 ______________________________________                                        Example 10  yes        >10 hours                                                          no         13 min                                                 Example 11  yes        >10 hours                                                          no         18 min                                                 Glass tube* --         12 min                                                 Glass tube**                                                                              --         43 min                                                 ______________________________________                                         *without treatment with silicone                                              **treated with silicone                                                  

EXAMPLE 14

A film was prepared from the hydrolyzed product of the allylidenediacetate-vinyl acetate copolymer. The hydrolyzed product has acroleinunit (6.9 mole %) and vinyl alcohol unit in the polymer. Byheat-treatment, the film became insoluble in water because of thecrystallization. The film was immersed in the heparin solutioncontaining 10,000 units for heparin for 30 min, which was adjusted at pH3.0 with H₂ SO₄. After being washed, the film was dried at ambienttemperature.

EXAMPLE 15

A copolymer comprising methyl methacrylate and methacrolein (6.1 mole %)was dissolved in acetone. Using this solution, a film was casted by theusual method. The film was immersed in the solution containing 50,000units of heparin for 40 minutes, adjusted at pH 2 with H₂ SO₄. The driedfilm was presented for non-thrombogenetic test.

EXAMPLE 16

The powdered copolymer of methylmethacrylate and methacrolein wassuspended in the aqueous solution containing 50,000 units of heparin at50° C. for one hour at pH 3.2 adjusted with H₂ SO₄. The polymer wasfiltered and dried. This was dissolved in acetone, and after theinsoluble part had been removed, the solution was casted to form a film.The film obtained was presented for non-thrombogenicity test.

EXAMPLE 17

A copolymer of acrylonitrile-methyl acrylate-methacrolein acetal (86:9:5by weight) was dissolved in dimethyl formamide. From the solution thusobtained, a film was prepared by casting the solution. The film wastreated in boiled water to remove traces of dimethyl formamide retainedin the film. This film was treated in the acidic aqueous solution having10,000 units of heparin and the film was presented for non-thrombogenictest.

EXAMPLE 18

A copolymer of acrylonitrile-vinyl acetate-p-formyl styrene (91:3:6) wasdissolved in dimethyl formamide. From this solution, a film was preparedin the same manner as in Example 17. Heparinization process was the sameas in Example 17.

EXAMPLE 19

From homogeneous blend of 30 parts of methyl methacrylatemethacroleincopolymer (84:16) and 70 parts of soft-polyvinyl chloride plasticizedwith DOP (dioctyl phthalate) a tube having inner diameter of 8 mm wasshaped. The tube was transparent and flexible. One end of the tube washeat-sealed to form a test tube. The test tube was filled with theheparin solution used in Example 17. After being stood over night at 30°C., the heparin solution was removed by decantation, and the tube wasdried.

EXAMPLE 20

The non-thrombogenic tests were performed according to the methoddescribed in Example 5 using the film specimens obtained in Examples 14to 18. The results are summarized in the below.

    ______________________________________                                                       Test I                                                         Test Specimen  Coagulation Time                                                                              Test II                                        Kind    Heparinized                                                                              Initial   Complete                                                                              Blood Mass                               ______________________________________                                        Example 14                                                                            yes        300 min   >10 hrs  3%                                              no          12 min   16 min  82%                                      Example 15                                                                            yes        260 min   >10 hrs  2%                                              no          8 min    19 min  89%                                      Example 16                                                                            yes        120 min   >10 hrs  8%                                              no          5 min    14 min  81%                                      Example 17                                                                            yes        280 min   >10 hrs  4%                                              no          6 min    12 min  86%                                      Example 18                                                                            yes        245 min   >10 hrs  2%                                              no          7 min    12 min  86%                                      Glass   --          6 min    12 min  100%                                     ______________________________________                                    

EXAMPLE 21

The non-thrombogenic test was performed by Lee-White Method using thetube obtained in Example 19. The result is shown with control data forcomparison.

    ______________________________________                                        Specimen                                                                      Kind        Heparinized                                                                              Coagulation Start Time                                 ______________________________________                                        Example 19  yes        >10 hrs                                                            no         14 min                                                 Glass tube* --          8 min                                                 Glass tube**                                                                              --         32 min                                                 ______________________________________                                         *without treatment with silicone                                              **treated with silicone                                                  

EXAMPLE 22

Cellulose acetate (Eastman Kodak Co., E-400-25) was dissolved inacetone-formamide mixture to form a spinning solution. The hollow fiberwas produced using a "tube-in-orifice" spinneret, namely, the spinningsolution was extruded through an annular slit, and simultaneously from atube which was placed at the center of the annular orifice, coresolution was introduced. The core solution (A) was a 20% aqueoussolution of CaCl₂, while core solution (B) has 0.5 mole/l sodium metaperiodate in addition to 20% of CaCl₂. The spinning method employed wasthe so called dry-jet wet spinning. The spun filament was introducedinto a water coagulation bath after passing through an air gap of 30 cm.The filament was washed with water, and then wound up on a reel. Thiswas immersed in water over night, during that period, gradients in thecore solution were dialyzed. In the inner surface of the hollow fiberprepared by using the core solution (B), the presence of aldehyde groupwas confirmed by infra-red spectrum. Interior surface of this hollowfiber was then treated with acidic (pH 2) heparin solution and thendried.

The Hemodialyzers were assembled using the fibers obtained in thisExample and, using each, blood dialysis was performed on a dog. Therewas observed non-thrombogenecity for the dialyzer assembled by use ofthe heparinized hollow fibers, while the hollow fiber withoutheparinization (using the core solution (A)) shows considerable bloodclotting.

EXAMPLE 23

The same spinning solution in example 22 was used. Ammonium chloride wasdissolved in 1 N HCl aqueous solution to form core solution (C). Tothis, 0.1 mole percent of periodic acid was added (core solution (D)).As in Example 22, the hollow fiber was prepared using the core solutions(C) and (D). The spinning was performed using usual dry-jet wet spinning(air gap: 30 cm) as in example 22. The hollow fiber obtained on the reelwas cut to be 30 cm long, then the core solution was removed from thehollow portion. The fiber was washed with water, followed by thetreatment with acidic (pH 2) heparin solution. Using the hollow fibersthus obtained, a hemodialyzer was assembled. The non-thrombogenenicproperties of the dialyzer were tested using a dog. The hollow fiberdialyzer using the heparinized hollow fibers obtained in this exampleshows no blood clotting.

EXAMPLE 24

Except for the use of the core solution having 0.1 mole of periodic salt(potassium periodate) in propylene glycol-water mixture (55:45), all theprocedure was the same as in Example 22. The hollow fibers wound up onthe reel was cut to be 30 cm long, then the core liquid was removed. Thefiber was then treated with dilute acetic acid, then washed with H₂ O,followed by the treatment with the heparin solution acidified with HCl.The hemodialyzer using this hollow fibers shows a minimum clotting ofthe blood, and outstanding effect of the present invention wasconfirmed.

What I claim is:
 1. A non-thrombogenic material comprising an aldehydegroup-containing polymer bonded directly with heparin in which at leastone hydroxyl group of said heparin is covalently bonded to one aldehydegroup of said polymer through only one acetal bond or hemiacetal bond ateach bonding site between said heparin and said polymer.
 2. Thenon-thrombogenic material according to claim 1 wherein said acetal orhemiacetal bond is formed by the reacting said heparin with said basepolymer containing an aldehyde group or an aldehyde group forming group.3. The non-thrombogenic material according to claim 2 wherein said basepolymer is prepared by polymerizing or copolymerizing a vinyl monomerhaving an aldehyde group or an aldehyde group-forming group and/or avinylidene monomer having an aldehyde group or an aldehyde group-forminggroup.
 4. The non-thrombogenic material according to claim 2 whereinsaid base polymer is prepared by cleaving a carbon-carbon bond of apolymer, said bond joining two carbon atoms, each of which is bonded toa hydroxyl group.
 5. The non-thrombogenic material according to claim 1wherein said hemiacetal bond is converted to a more stable acetal bondby eliminating a water molecule or an alcohol molecule.
 6. Thenon-thrombogenic material according to claim 2 wherein said aldehydegroup of said base polymer is converted to an acetal or hemiacetal groupin the presence of an alcohol and then reacted with said heparin.
 7. Thenon-thrombogenic material according to claim 1 wherein said polymercontains aldehyde groups or aldehyde group-forming groups in the rangeof 1.0 to 20.0% by weight of said polymer, and said heparin is used as asolution having 50 to 100,000 USP units of heparin when applied to saidreaction.
 8. A non-thrombogenic material comprising a base polymer, saidbase polymer containing: (a) two vicinal carbon atoms, each containing ahydroxyl group; or (b) two hydroxyl-substituted carbon atoms withanother carbon atom therebetween, said base polymer having been bondeddirectly with a heparin derivative containing aldehyde groups in whichat least one aldehyde group of said heparin is covalently bonded to onehydroxyl group of said base polymer through only one acetal bond orhemiacetal bond at each bonding site between said heparin derivative andsaid base polymer.
 9. The non-thrombogenic material of claim 1 in whichsaid aldehyde group is formed by cleaving a carbon-to-carbon bond of avic-glycol type polymer with periodic acid, a salt of periodic acid orlead tetraacetate.
 10. The non-thrombogenic material of claim 8 in whichthe aldehyde groups of the heparin are formed by cleavingcarbon-to-carbon bonds of heparin with periodic acid, a salt of periodicacid or lead tetraacetate.
 11. The non-thrombogenic material accordingto claim 8 wherein said heparin derivative containing aldehyde group isformed by cleaving a carbon-carbon bond of heparin having vicinalhydroxyl groups thereat.